Method for inspecting defect and system therefor

ABSTRACT

Based on a plurality of defects&#39; position-coordinates and attribute detected by an inspecting apparatus, defects that are easily detectable by an observing apparatus are selected. With these selected defects employed as the indicator, the observing apparatus detects and observes the defects. Moreover, creating a coordinate transformation formula for representing a correlated relationship in the defects&#39; position-coordinates between both the apparatuses, the observing apparatus transforms the defects&#39; position-coordinates so as to observe the defects.

This is a continuation of application Ser. No. 10/888,021 filed 12 Jul.2004 now U.S. Pat. No. 7,010,447, which is a continuation of applicationSer. No. 09/794,532 filed 27 Feb. 2001, now U.S. Pat. No. 6,792,359,which claims priority to Japanese Patent Application No. 2000-231352filed 26 Jul. 2000, the contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a defect inspecting method and a defectinspecting system for the inspection of defects existing on a substrate.Here, examples of the substrate are a semiconductor wafer and a maskused for the fabrication of a semiconductor device.

An inspecting apparatus or the like allows the detection of the defectsthat exist on the substrate such as the semiconductor wafer and themask. Moreover, the use of an observing apparatus allows observing thedetails of the defects, collecting the observed images thereof, andanalyzing the defects. In the defect inspecting system like this, theobserving apparatus is required to be able to promptly execute thepositioning as to where the defects detected by the inspecting apparatusexist on the substrate.

Conventionally, as a method of observing the defects on the substrate,there has been known the following method: The substrate as a whole or aportion thereof is inspected in advance so as to confirm whether or notthe defects exist. Then, the positions of the defects thus found arestored as their coordinates on the substrate. Next, these storedcoordinates are inputted into the observing apparatus through acommunications member or a storage medium. Finally, based on thecoordinates, the position-alignment is performed so that the defectswill enter an observing field-of-view of the observing apparatus, thenexecuting the observation.

At this occasion, if it is the case where the inspecting apparatus andthe observing apparatus co-use the same substrate holding mechanism andsubstrate displacing mechanism and where the substrate remains held bythe substrate holding mechanism at the time of transition from theinspection to the observation, simply displacing the observingfield-of-view to the specified position-coordinates is enough for theposition-alignment toward the observing apparatus. Accordingly, it isquite easy to permit the defects to enter the field-of-view.

In many cases, however, the inspecting apparatus requested to have ahigh throughput and the observing apparatus requested to have a highobserving resolution are different apparatuses. Consequently, the easyposition-alignment in the observing apparatus as described above is adifficult task. This requires the sharing of the coordinate system onthe substrate by the inspecting apparatus and the observing apparatusthrough the use of some kind of method. Thus, for example, the followingprocessing is executed: Positions of predetermined plurality of pointson the substrate are detected using the inspecting apparatus and theobserving apparatus. Then, the coordinate systems characteristic of therespective apparatuses are corrected based on this detection result,thereby causing the substrate coordinate system to be shared by both ofthe apparatuses.

As the concrete method therefor, there have been known the followingmethods, for example: A method in which the plurality of points providedalong the circumference of the substrate and becoming a criterion of thepositioning are constrained mechanically by the substrate holdingmechanism, or a method in which an image of a predetermined patternexisting beforehand on the substrate is detected and the coordinatesystems are corrected based on the position of this pattern.

JP-A-3-156947 has disclosed one example of the methods in which there isused the coordinate system that is common to a plurality of apparatusesincluding the inspecting apparatus and the observing apparatus.

In the above-described prior art method of mechanically constraining thepoints on the substrate, there exists a problem in the mechanicalposition reproducibility, i.e., the dimension accuracy. For example, itis difficult to implement the high-accuracy position-alignment at alevel of micrometers.

Also, concerning the above-described method of correcting the coordinatesystems in accordance with the detected pattern position, the method isinapplicable to, for example, the substrate before the pattern'sformation of course. Moreover, when, for example, the inspectingapparatus is an optical type and the observing apparatus is anelectron-beam type, i.e., the pattern detecting methods and the patterndetecting accuracies are different between both of the apparatuses,there exists the case where it is impossible to detect the same patternin common to the apparatuses. Accordingly, the method is inapplicable tothis case.

For example, when the substrate is covered with a transparent oxide-filmand a pattern-existing under the oxide-film is used for theposition-alignment of the optical type inspecting apparatus, it isdifficult to detect the pattern with the use of the electron-beam typeobserving apparatus.

JP-A-11-167893 has disclosed one example of the methods of detectingforeign substances in the case where the detecting methods are differentbetween the inspecting apparatus and the observing apparatus. In thisexample, using both the coordinate values of the foreign substances onthe substrate and the coordinate values thereof on the stage, it isintended to implement the sharing of the coordinate system between theinspecting apparatus and the observing apparatus. This makes it easierfor the observing apparatus to find out the foreign substances that havebeen detected by the inspecting apparatus. Furthermore, the detectedforeign substances are automatically selected depending on thecharacteristics such as the size, thereby enhancing the reliability of acorrecting formula for the sharing of the coordinate system.

However, even if the inspecting apparatus and the observing apparatusemploy the detecting methods similar to each other, when, for example,trying to observe into what form the defects detected at the time of theinspection have changed after the inspected substrate had been subjectedto several processing steps, the pattern turns out to exist under a filmformed at the processing steps. Consequently, it becomes impossible todetect the same pattern.

SUMMARY OF THE INVENTION

It is an object of the present invention to implementefficiency-heightening and time-shortening of a defect observingoperation, a defect image collecting operation, and a defect analyzingoperation.

Also, it is another object of the present invention to allow ashort-time and high-efficiency defect observation to be executed whenthe inspecting method and the observing method differ from each other.

Conventionally, when the substrate before the pattern's formation isinspected and observed, or when the inspecting apparatus and theobserving apparatus are unable to detect the same pattern, it wasdifficult to cause the defects detected by the inspecting apparatus toenter the observing field-of-view of the observing apparatus with ahigh-accuracy. As the countermeasures against this, for example, thefollowing attempts have been made: The defects are searched for in sucha manner as to reduce the observing magnification of the observingapparatus to a lower magnification, or the operator searches for thedefects with the high magnification left unchanged. In such operations,however, there existed a problem of taking so much labor and time.

Also, conventionally, when the optical conditions employed differbetween the inspecting method and the observing method, it was notnecessarily easy for the observing apparatus to observe the defectcandidates that have been detected by the inspecting apparatus. As aresult, there existed a problem of spending wasted time in changing theobserving conditions or making a search around where the defects exist.

When the observing apparatus performs the observation, the collection ofthe observed images, and the defect analysis toward the defects detectedby the inspecting apparatus, the present invention executes theposition-alignment toward the detected defects with a high-accuracy.This allows the images to be detected at a time with a highermagnification, thereby implementing the efficiency-heightening and thetime-shortening of the defect observing operation, the defect imagecollecting operation, and the defect analyzing operation.

Also, when the inspecting method and the observing method differ fromeach other, the present invention excludes, from the inspection result,a defect candidate the detection of which is impossible by the observingmethod, thereby making it possible to execute the short-time andhigh-efficiency defect observation.

According to the embodiments of the present invention, in addition toin-substrate coordinate system plurality of defects'position-coordinates detected and extracted by the inspecting apparatus,attribute of the defects is outputted. Here, examples of the attributeare as follows: The dimension, the type, the scattered light amount,local variation in the luminance, the profile configuration, and so on.

Next, based on the defects' position-coordinates and the defects'attribute inputted from the inspecting apparatus, a plurality of defectsthat are judged to be easily detectable by the observing apparatus areselected. Then, based on the selected defects' position-coordinates, theimage detection is performed by the observing apparatus so as to findout the defects. Moreover, based on the defects' positions within theimage, in-substrate coordinate system defects' position-coordinatesdefined on the observing apparatus side are calculated. Since,essentially, the substrate coordinate system is fixed onto thesubstrate, the in-substrate coordinate system represented defects'position-coordinates defined on the inspecting apparatus side andinputted from the inspecting apparatus should completely coincide withthe in-substrate coordinate system defects' position-coordinates definedon the observing apparatus side.

As described earlier, however, the approximate position-alignment hasbeen made where the mechanical position-alignment mechanism using, forexample, the substrate circumference or the like makes it unhopeful toexpect the high-accuracy. Consequently, it is usual at this point intime that the substrate coordinate system defined on the observingapparatus side differs from the substrate coordinate system defined onthe inspecting apparatus side.

Accordingly, based on the in-substrate coordinate system defects'position-coordinates defined on the observing apparatus side and thein-substrate coordinate system defects' position-coordinates defined onthe inspecting apparatus side and inputted from the inspectingapparatus, a coordinate transformation from the substrate coordinatesystem defined by the inspecting apparatus to the substrate coordinatesystem defined by the observing apparatus is derived with respect to thedefects selected by the inspecting apparatus.

In accordance with this coordinate transformation, the defects'position-coordinates inputted from the inspecting apparatus aretransformed into the position-coordinates in the substrate coordinatesystem defined by the observing apparatus. Hereinafter, the defectobservation and the like will be executed based on these transformedposition-coordinates.

Also, information on this coordinate transformation is saved and storedin a database with a set of the inspecting apparatus and the observingapparatus regarded as the unit. When executing the observation at thenext opportunity, the position-alignment is performed first, using theinformation on this coordinate transformation. If a new coordinatetransformation is derived by the above-described method, theabove-described information on the coordinate transformation is updated.

In the present invention, the defects that actually exist on thesubstrate and are easily detectable in common by the observing apparatusare selected, then being used as the criterion of the substrateposition-alignment. Consequently, even when there exists no pattern forthe position-alignment, or even when, if any, the pattern is unable tobe used in common to the inspecting apparatus and the observingapparatus, it becomes possible for the observing apparatus to executethe position-alignment toward the defects' positions with ahigh-accuracy.

Also, in the present invention, based on the defects'position-coordinates and the defects' attribute, only the defects thatare judged to be easily detectable by the observing apparatus areobserved. This makes the efficient defect observation possible.

Furthermore, the information on the coordinate transformation betweenthe inspecting apparatus and the observing apparatus is stored in thedatabase for use, or the information is updated. This makes it possibleto always execute the defect observation based on a more precisepositioning.

As described earlier, when the observing apparatus performs theobservation, the collection of the observed images, and the defectanalysis toward the defects detected by the inspecting apparatus, thepresent invention executes the position-alignment toward the detecteddefects with a high-accuracy. This allows the images to be detected at atime with a higher magnification, thereby making it possible toimplement the efficiency-heightening and the time-shortening of thedefect observing operation, the defect image collecting operation, andthe defect analyzing operation.

Also, when the inspecting method and the observing method differ fromeach other, the present invention excludes, from the inspection result,a defect candidate the detection of which is impossible by the observingmethod, thereby making it possible to provide the method of executingthe short-time and high-efficiency defect observation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual diagram for illustrating the configuration of adefect inspecting system;

FIG. 2 is a side view for illustrating the configuration of a mainportion of the inside of an inspecting apparatus;

FIG. 3 is a plan view for illustrating an example of the state where asemiconductor wafer is installed on the inspecting apparatus;

FIG. 4 is a plan view for illustrating an example of the state where thesemiconductor wafer is installed on the inspecting apparatus;

FIG. 5 is a side view for representing the configuration of a scanningtype electron microscope, using the partially transverse cross section;

FIG. 6 is a flow chart for showing the procedure of an inspectingmethod;

FIG. 7 is a flow chart for showing the procedure of an inspectingmethod;

FIG. 8 is a conceptual diagram for illustrating the configuration of adefect inspecting system;

FIG. 9 is a side view for illustrating the configuration of a mainportion of the inside of an optical type inspecting apparatus; and

FIG. 10 is a screen diagram for illustrating an example of a screendisplay.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIGS. 1 to 7, the explanation will be given belowconcerning the 1st embodiment of the present invention. FIG. 1 is aconceptual diagram for illustrating the configuration of a defectinspecting system.

In the present embodiment, the target to be inspected is a semiconductorwafer before a pattern's formation by etching. Using an inspectingapparatus 1 that is an optical type inspecting apparatus using thedetection of scattered laser light, defects on the surface areinspected. Then, observing the defects is performed using an observingapparatus 2 that is a scanning type electron microscope. Although, inthe present embodiment, foreign substances are considered as the exampleof the defects, the same concept as here also makes it possible todetect and observe pattern defects such as shorts or deficits in acircuit pattern.

FIG. 2 illustrates the configuration of a main portion of the inside ofthe inspecting apparatus 1 illustrated in FIG. 1. FIG. 3 is a plan viewfor illustrating an example of the state where a semiconductor wafer 3,i.e., the inspection target, is installed on the inspecting apparatus 1.FIG. 4 is a plan view for illustrating an example of the state where,similarly, the semiconductor wafer 3, i.e., the inspection target, isinstalled on the inspecting apparatus 1.

In the inspecting apparatus in FIG. 2, the irradiation with laser lightis performed from an oblique direction by a laser 9, and the scatteredlaser light 10 is detected from above (or obliquely) by a detector 11.Displacing stages 12 a, 12 b allows a plurality of foreign substances tobe detected all over the entire surface of the semiconductor wafer 3.The light amounts detected by the detector 11 are binarized by abinarizer 14. Then, binarized light amounts that exceed a predeterminedthreshold value 13 are regarded as the foreign substances, then beingextracted as the defects.

In accordance with stage control information 18 from a stage controller15, these defects' position-coordinates 4 in the coordinate system xyare outputted from a foreign substance defect judging unit 16. Moreover,at this time, the scattered light amounts are outputted together asattribute 5 of the defects by an attribute judging unit 17.

In this case, the coordinate system xy fixed onto the semiconductorwafer 3 can be determined mechanically by positioning pins 8 a, 8 b, 8 cand so on that are provided in a unit such as a wafer holder on thestage 12 b. This is performed using, as illustrated in FIG. 3, a notch6, i.e., an incision portion of the semiconductor wafer 3, or using, asillustrated in FIG. 4, an orient flat in the straight line portion,i.e., an orifla 7. Also, concrete examples of the attribute 5 are thedimension, the type, the scattered light amount, and so on.

Next, using the defects' position-coordinates 4 and the defects'attribute 5 obtained in this way, the position-alignment toward thedefects at the time of observing the detects is performed. This isperformed subsequently to the inspection of the defects. FIGS. 6, 7 areflow charts for showing the procedures of the inspecting method.

At a step 601 in FIG. 6 and in FIG. 1, the plurality of defects'position-coordinates 4 and the defects' attribute 5 are extracted ordetermined by the inspecting apparatus 1, then being once stored into adatabase 103 through a communications member 102 such as an areanetwork, an intranet, and the Internet. The defects'position-coordinates 4 and the defects' attribute 5 are read out throughthe communications member 102 when necessary. Incidentally, they neednot necessarily be read out through the communications member 102.Sending or receiving the information may also be performed using astorage medium such as a magnetic disk or an optical disk.

Next, at a step 602, from among the above-described defects and takingadvantage of the defects' attribute 5, defects that are detectable bythe observing apparatus 2 are selected. For example, taking advantage ofthe fact that there exists a certain correlated relationship between thescattered laser light amounts and the sizes of the foreign substances,i.e., the defects, a defect selecting unit 100 illustrated in FIG. 1selects foreign substances the scattered light amounts of which areequivalent to a size within a certain fixed criterion that is detectableby the observing apparatus 2, i.e., for example, a size in the rage of 1μm to 3 μm. Next, at a step 603, the observing apparatus 2 detects theselected defects, thereby calculating their position-coordinates 104.Next, at a step 604, from the defects' position-coordinates 104 detectedby the observing apparatus 2 and the defects' position-coordinates 4extracted by the inspecting apparatus 1, a coordinate-correspondencedetermining unit 101 calculates information 401 on a correlatedrelationship between the coordinate systems in the detect observation.

At a step 605, together with a set of the respective identificationnumbers (or symbols) of the inspecting apparatus 1 and the observingapparatus 2, this correlated relationship information 401 is sent to thecommunications member 102, then being stored into the database 103.Every time observing a sample such as the substrate is performed, thecorrelated relationship information 401 is calculated in accordance withthe same steps as those described above, and the correlated relationshipinformation 401 stored in the database 103 is updated.

Incidentally, the database 103 into which the correlated relationshipinformation 401 is stored may be directly connected to thecoordinate-correspondence determining unit 101 without the linkage ofthe communications member 102. Also, in the above-described detectobservation, if the correlated relationship information 401 between thecoordinate systems has been already stored in the database 103 thedefects' position-coordinates 4 from the inspecting apparatus 1 may becorrected using the information for their use at the time of theobservation.

In this way, the above-described selection is executed using theattribute 5 of the defects that are assumed to be easily detectable. Theselection may be performed by the inspecting apparatus 1. Also, usingthe defects' attribute 5 outputted from the inspecting apparatus 1, theselection may be performed by another apparatus. Moreover, fetching thedefects' attribute 5 into the observing apparatus 2, the selection maybe performed by the observing apparatus 2.

Next, using the correlated relationship information 401 stored in thedatabase 103, the explanation will be given concerning a method ofdetecting a desired defect using the observing apparatus 2.

In FIG. 7, at a step 701, the coordinate-correspondence determining unit101 receives, through the communications member 102, theposition-coordinates 4 and the attribute 5 of the defects that have beenselected as being detectable by the observing apparatus 2 from among theplurality of defects detected by the inspecting apparatus 1 and storedin the database 103 at the step 601 in FIG. 6. Next, at a step 702, thecoordinate-correspondence determining unit 101 calculatesposition-coordinates 105 transformed from the defects'position-coordinates 4 in accordance with the correlated relationshipinformation 401 stored in the database 103, then sending the transformedposition-coordinates 105 to the observing apparatus 2. At a step 703,based on the above-described defects' transformed position-coordinates105, the observing apparatus 2 detects the defects. Moreover, at a step704, employing the detected defects as the indicator, the observingapparatus 2 detects and observes the desired defect wished to beobserved in detail.

In the present embodiment, the above-described processings in the defectselecting unit 100 and the coordinate-correspondence determining unit101 are set to be a mode carried out by a software system.

Next, the explanation will be given concerning an embodiment where thescanning type electron microscope is employed as the observing apparatus2 in FIG. 1. FIG. 5 is a side view for representing the configuration ofthe scanning type electron microscope, i.e., the observing apparatus 2,using the partially transverse cross section.

An electron-beam emitted from an electron source 20 is deflected in thex, y directions by a deflector 21. When scanning the semiconductor wafer3 using the electron-beam converged by a converging lens 22, secondaryelectrons are generated. Then, the secondary electrons are convertedinto an electrical signal by a detector including a scintillator 23 anda photomultiplier tube 24. Next, this electrical signal is outputted toa display 26 that is synchronized with the deflection of theelectron-beam by a synchronizer 25, thereby obtaining a 2-dimensionalelectron-beam image. Changing the deflection width of the electron-beammakes it possible to easily change the magnification of the2-dimensional electron-beam image.

A stage controller 28 sends, to a defect position determining unit 29,the defects' position-coordinates 4 sent from the defect selecting unit100 in FIG. 1, the transformed position-coordinates 105 sent from thecoordinate-correspondence determining unit 101, and stage controlinformation 19 for controlling the positions of stages 27 a, 27 b.

The defect position determining unit 29 calculates the defects'position-coordinates 104 from the electron-beam' position informationfrom the synchronizer 25 and the information from the stage controller28, then sending the position-coordinates 104 to thecoordinate-correspondence determining unit 101 in FIG. 1.

Also, the electrical signal detected by the detector including thescintillator 23 and the photomultiplier tube 24 is digitized using an ADconverter (not illustrated). Then, using a communications member 200such as an intranet or the Internet, the digitized signal is stored intoa database 201 in a state of being related with the position-coordinatesand so on. This makes it possible to save and reuse the imageinformation.

Here, although there has been illustrated the embodiment where thedatabase 201 is located outside the observing apparatus 2 and theinformation is transmitted using the communications member 200, thedatabase 201 may be located inside the observing apparatus 2. Also,instead of using the database 201, the information may be stored in astorage medium such as a memory.

Concerning the positioning of the semiconductor wafer 3 in the observingapparatus 2, the following can be considered: The positioning by themechanical method such as the one using the positioning pins illustratedin FIGS. 3, 4 as is the case with the inspecting apparatus 1, or inaddition to this, the positioning by a method of observing a positioningmark so as to determine the coordinate system of the inspection target.In the present embodiment, since the semiconductor wafer before thepattern's formation is employed as the inspection target, no positioningmark has been formed. Accordingly, there has been used the positioningby the mechanical method such as the positioning pins.

The coordinate system determined here is the coordinate system that ischaracteristic of the inspection target. Thus, essentially, thecoordinate system is calculated in such a manner that it becomesidentical to the coordinate system determined by the inspectingapparatus 1. In many cases, however, the positioning method in theobserving apparatus 2 (in this case, positions of the positioning pinsor the like) is not always the same as the positioning method in theinspecting apparatus 1. In addition, an error at the time of determiningthe coordinate system exists in both the inspecting apparatus 1 and theobserving apparatus 2. As a result, the coordinate system determined bythe observing apparatus 2 does not completely coincide with thecoordinate system determined by the inspecting apparatus 1.Consequently, even if, using directly the defects' position-coordinates4, i.e., the output from the inspecting apparatus 1, an attempt todetect the image is made by displacing the stages 27 a, 27 b of thescanning type electron microscope, i.e., the observing apparatus 2, anddisplacing the observing field-of-view, in many cases, the attemptproves to be unsuccessful in finding out the defects in the center ofthe observing field-of-view.

In view of this situation, at first, limiting the above-describeddefects to the defects selected by the defect selecting unit 100illustrated in FIG. 1, detecting the defects' image is performed. Asdescribed earlier, the defects selected by the defect selecting unit 100are the plurality of defects which are selected in accordance with thecriterion of being easily detectable by the observing apparatus 2 andthus the size of which is equal to, for example, 1 μm or more. As aresult, their existences can be confirmed easily even in a lowermagnification of an order of guaranteeing that the defects securelyenter the field-of-view, for example, a magnification of 5000 times orless. Also, since the upper limit of the selected defects' size has beendefined, the defects never extend off the field-of-view. In this case,as a method of automatically recognizing the defects' positions from thedetected image, there exists the method of recognizing the defects'positions from whether the luminance of the detected image is simplybrighter or darker in comparison with the periphery thereof.

When the selected defects are unable to be detected by the observingapparatus 2 even if the above-described method is employed and executed,the defects are excluded from the selection. Also, if the relationshipbetween the coordinate system determined by the inspecting apparatus 1and the coordinate system determined by the observing apparatus 2 hasbeen stored in advance in the database 103, by executing the coordinatetransformation through the use of this relationship, the defects may bedetected again.

In this way, concerning the defects selected as the one that should bedetected first by the observing apparatus 2 from among the defectsdetected by the inspecting apparatus 1, there can be obtained a pair ofthe defects' position-coordinates 4 (x, y) in the inspection targetcoordinate system xy determined by the inspecting apparatus 1 and thedefects' position-coordinates 104 (x′, y′) in the inspection targetcoordinate system x′y′ determined by the observing apparatus 2. CreatingN sets of the pairs and using a coordinate group including these N setsof pairs (x_(i), y_(i)) (x′_(i), y′_(i)) (i=1, 2, . . . , N), thetransformation formula from the coordinate system determined by theinspecting apparatus 1 to the coordinate system determined by theobserving apparatus 2 is derived.

For example, designating, as formula 1, the transformation formulabetween the coordinate system xy determined by the inspecting apparatus1 and the coordinate system x′y′ determined by the observing apparatus2, least-squares approximation method is employed. Thus, after partiallydifferentiating ε² defined by formula 2 by a₁₁, a₁₂, a₂₁, a₂₂, x₀, andy₀, respectively, the obtained results are set to be=0 and solved. Thisallows the respective coefficients a₁₁, a₁₂, a₂₁, a₂₂, x₀, and y₀ to bedetermined from two sets of three-solution simultaneous linearequations, i.e., formulae 3, 4.x′=a ₁₁ x+a ₁₂ y+x ₀y′a ₂₁ x+a ₂₂ y+y ₀  [formula 1]

$\begin{matrix}{ɛ^{2}{\sum\limits_{i}^{\;}\;\begin{bmatrix}{\left\{ {X_{1}^{\prime} - \left( {{a_{11}x_{i}} + {a_{12}y_{i}} + x_{o}} \right)} \right\}^{2} +} \\\left\{ {y_{i}^{\prime} - \left( {{a_{21}x_{i}} + {a_{22}y_{i}} + y_{0}} \right)} \right\}^{2}\end{bmatrix}}} & \left\lbrack {{formula}\mspace{14mu} 2} \right\rbrack\end{matrix}$

$\begin{matrix}{{\begin{pmatrix}{\sum\limits_{i}^{\;}\; x_{i}^{2}} & {\sum\limits_{i}^{\;}\;{x_{i}y_{i}}} & {\sum\limits_{i}^{\;}\; x_{i}} \\{\sum\limits_{i}^{\;}\;{x_{i}y_{i}}} & {\sum\limits_{i}^{\;}\; y_{i}^{2}} & {\sum\limits_{i}^{\;}\; y_{i}} \\{\sum\limits_{i}^{\;}\; x_{i}} & {\sum\limits_{i}^{\;}\; y_{i}} & {\sum\limits_{i}^{\;}\; 1}\end{pmatrix}\begin{pmatrix}a_{11} \\a_{12} \\x_{0}\end{pmatrix}} = \begin{pmatrix}{\sum\limits_{i}^{\;}\;{x_{i}^{\prime}x_{i}}} \\{\sum\limits_{i}^{\;}\;{x_{i}^{\prime}y_{i}}} \\{\sum\limits_{i}^{\;}\; x_{i}^{\prime}}\end{pmatrix}} & \left\lbrack {{formula}\mspace{14mu} 3} \right\rbrack\end{matrix}$

$\begin{matrix}{{\begin{pmatrix}{\sum\limits_{i}^{\;}\; x_{i}^{2}} & {\sum\limits_{i}^{\;}\;{x_{i}y_{i}}} & {\sum\limits_{i}^{\;}\; x_{i}} \\{\sum\limits_{i}^{\;}\;{x_{i}y_{i}}} & {\sum\limits_{i}^{\;}\; y_{i}^{2}} & {\sum\limits_{i}^{\;}\; y_{i}} \\{\sum\limits_{i}^{\;}\; x_{i}} & {\sum\limits_{i}^{\;}\; y_{i}} & {\sum\limits_{i}^{\;}\; 1}\end{pmatrix}\begin{pmatrix}a_{21} \\a_{22} \\y_{0}\end{pmatrix}} = \begin{pmatrix}{\sum\limits_{i}^{\;}\;{y_{i}^{\prime}x_{i}}} \\{\sum\limits_{i}^{\;}\;{y_{i}^{\prime}y_{i}}} \\{\sum\limits_{i}^{\;}\; y_{i}^{\prime}}\end{pmatrix}} & \left\lbrack {{formula}\mspace{14mu} 4} \right\rbrack\end{matrix}$

In this case, focusing the defects even further and selecting thedefects so that the defects will distribute all over the entire surfaceof the inspection target uniformly, the detection by the observingapparatus 2 is performed. This makes it possible to enhance thetransformation formula's accuracy and to shorten the image detectingtime and the image calculating time.

Now, using the transformation formula determined in this way, asillustrated in FIG. 1, all the defects' position-coordinates 4 outputtedfrom the inspecting apparatus 1 are transformed into theposition-coordinates in the coordinate system determined by theobserving apparatus 2. Taking advantage of the transformedposition-coordinates 105, the position-alignment of the semiconductorwafer 3 toward the coordinates' positions is performed by the stages 27a, 27 b. Then, the image detection is performed with the magnificationenhanced up to, for example, 20000 times or more. This makes it possibleto observe all the detected defects in detail or to record the detailedobserved image.

According to the present embodiment of the present invention, even inthe case of the semiconductor wafer before the pattern's formation, itbecomes possible to execute the short-time and detailed observation ofthe foreign substances, the defects, or the like

Observing the defects on the semiconductor wafer is executed using thedefect inspecting method or the defect inspecting system as describedabove. This allows the cause of a defect occurrence to be discovered inthe fabrication process of semiconductor devices in an early time,thereby making it possible to obtain the semiconductor devices with anexcellent yield.

Next, referring to FIGS. 8 to 9, the explanation will be given belowconcerning the 2nd embodiment of the present invention. As is the casewith FIG. 1, FIG. 8 is a conceptual diagram for illustrating theconfiguration of a defect inspecting system, and FIG. 9 is a side viewfor illustrating the configuration of a main portion of the inside of anoptical type inspecting apparatus.

Although, in the present embodiment as well, a semiconductor wafer isemployed as the inspection target, the semiconductor wafer is apattern-formed wafer on which a pattern, such as a pattern by etching ora resist pattern, has been formed.

In the defect inspecting system illustrated in FIG. 8, using an opticaltype inspecting apparatus 301 using the image detection and the imagecomparison based on a bright field-of-view illumination, the detectionis performed concerning pattern defects such as shorts or deficitsformed on the semiconductor wafer, or foreign substances on the patternsurface. Then, observing the defects is performed using the scanningtype electron microscope that is the observing apparatus 2.

In FIG. 9, the semiconductor wafer 3 is inspected by the optical typeinspecting apparatus 301. Then, the detected defectsposition-coordinates 4 are outputted as the coordinates based on thecoordinate system xy fixed onto the semiconductor wafer 3, i.e., theinspection target substrate. Also, the defects' attribute 5 detectedwith the defects' position-coordinates 4 are outputted together. In thiscase, as is the case with the coordinate systems illustrated in FIG. 3or 4 and described in the 1st embodiment of the present invention, thecoordinate system xy fixed onto the semiconductor wafer 3, after beingdetermined mechanically by the positioning pins and so on using thenotch 6 or the orifla 7 of the semiconductor wafer 3, is determinedprecisely by observing a positioning mark that is formed at apredetermined position and with a predetermined configuration on thesemiconductor wafer 3.

In the optical type inspecting apparatus 301, as illustrated in FIG. 9,the irradiation with illuminating light is performed from anilluminating light source 302 onto the semiconductor wafer 3, using alens 304 a from above. Then, the reflected light is detected through alens 304 b by an image censor 303 positioned above. Displacing stages312 a, 312 b allows the image to be detected all over the entire surfaceof the semiconductor wafer 3.

On the pattern-formed wafer 3, there exist repeated patterns the unit ofwhich is equal to a light exposure unit at the time when the pattern isexposed to light or is equal to a value obtained by dividing the lightexposure unit by an integer. Each repeated pattern exists for each die,or for each memory cell within a die. In the inspection, a delayquantity corresponding to a repeated spacing between these repeatedpatterns is created using a memory 305. Then, using a comparator 306,the delay quantity is compared with an image detected as a referenceimage. Next, the cases where the difference therebetween is judged to belarger than a certain fixed threshold value 313 by a binarizer 314 aredetected as the defects. In addition, the defects' position-coordinates4 in the coordinate system xy are caused to correspond to stage controlinformation from a stage controller 315 and the defects' positions onthe image, then being outputted from a defect judging unit 316.Moreover, the defects' attribute 5 is outputted together therewith by anattribute judging unit 317.

As a method of outputting the attribute of a detected defect, thereexists a method of outputting the size of the defect as one attribute.In the above-described optical type inspecting apparatus 301, at thetime of the image detection, the image detection is performed as anaggregation of the luminances of detecting units called pixels. Thus,for example, a defect detected as the non-coincidence between therepeated patterns by the image comparison can also be expressed byemploying the pixel as the unit. Accordingly, the area can be expressedusing the number of the pixels, and the dimension or the size thereofcan also be expressed using the number of the pixels in thelongitudinal, the transverse, or the longer-axis direction.Consequently, in the case of using the size of the defect as thedefect's attribute, when the dimension within a fixed certain range, forexample, a range of 0.7 μm to 2 μm, is employed as the criterion and thedefects' positions included in this range are searched for by the imagedetection performed by the observing apparatus, the luminances and thenumber are detected in the pixel unit. As a result, even in a lowermagnification, it becomes possible to find out the defect surely andwithout fail.

Also, as the defect's attribute other than the size, there can also beused, for example, local variation in the luminance of the detecteddefect portion. Namely, for example, the summation is taken concerningthe difference between the maximum value and the minimum value in eachportion of 2×2 pixels within the detected defect' region, and then thesummation is normalized by being divided by the defect's size (i.e., thenumber of the pixels). This makes it possible to judge so-called “degreeof roughness” of the defect. Also, as still another attribute, thesquare of the detected defect' profile length is divided by the areaand, from to what extent the resultant value is large or small, itbecomes possible to judge so-called “degree of serration” of the profileconfiguration. A defect with a large amount of the “degree of roughness”or the “degree of serration” is, in many cases, a defect exposed ontothe surface of the inspection target. On account of this, utilizing the“degree of roughness” or the “degree of serration” makes it possible tojudge whether the defect is positioned inside the inspection target oris exposed on the surface thereof.

In the present embodiment in particular, the scanning type electronmicroscope is employed as the observing apparatus 2. Accordingly, it ishighly likely that the defect is unobservable unless exposed onto thesurface, and thus these attributes are effective. The defect informationfrom the optical type inspecting apparatus 301 is sieved and selectedusing the attributes, and only the defects that are observable by thescanning type electron microscope are extracted and observed, therebyallowing the observing time to be shortened.

Next, in FIG. 8, using the defects' position-coordinates 4 and thedefects' attribute 5 obtained in this way, the position-alignment towardthe defects in the defect observation is performed with a high-accuracy.This is performed subsequently to the inspection of the defects. In thiscase, the defects' position-coordinates 4 and the defects' attribute 5are sent to the defect selecting unit 100 and thecoordinate-correspondence determining unit 101, using a storage mediumor a communications member such as an intranet or the Internet. Ofcourse, a database may be provided in the communications member, andsending or receiving the data may also be performed through the member.

At first, by the defect selecting unit 100, the defects, the sizes ofwhich are included within the above-described certain fixed criterionand the “degree of roughness” and the “degree of serration” of whichexceed a certain fixed criterion, are assumed to be easily detectable inthe defect observation and are selected. Then, in the defectobservation, the observing apparatus 2 detects the selected defects.

Next, from the defects' position-coordinates 104 determined by theobserving apparatus 2 and the defects' position-coordinates 4 by theinspecting apparatus 301, the coordinate-correspondence determining unit101 determines a correlated relationship between the coordinate systemsin the detect observation.

In this way, the above-described selection can be executed using theattribute of the defects that are assumed to be easily detectable. As isthe case with the 1st embodiment, the selection may be performed by theinspecting apparatus 301, or may be performed by another apparatus usingthe attribute outputted from the inspecting apparatus 301. Moreover,fetching the attribute into the observing apparatus 2, the selection maybe performed by the observing apparatus 2. In the present embodiment,the above-described processings are executed by a software systemprovided in the defect selecting unit 100 and thecoordinate-correspondence determining unit 101 illustrated in FIG. 8.

In the present embodiment, the scanning type electron microscopeemployed as the observing apparatus 2 is of the same configuration andoperation as those of the scanning type electron microscope in the 1stembodiment one example of which has been illustrated in FIG. 5.

In the observing apparatus 2 as well, as is the case with the opticaltype inspecting apparatus 301, the coordinate system of the inspectiontarget is determined based on the positioning by the mechanical methodsuch as the one using the positioning pins on the semiconductor wafer,or in addition to this, based on the method of observing a positioningmark or the like. In the present embodiment, the semiconductor waferafter the pattern's formation is employed as the inspection target.Accordingly, the positioning mark, which has been formed on thesemiconductor wafer, can be used for determining the coordinate systemof the inspection target.

At this time, there exists no problem if determining the coordinatesystem is possible using the same positioning mark as that used in theoptical type inspecting apparatus 301. If, however, this mark existsunder an oxide-film insulating layer or the like and thus detecting themark by an electron-beam is difficult, it turns out that anotherpositioning mark that exists in the uppermost layer and is easy todetect will be used. Consequently, in this case, as is the case with the1st embodiment, an error at the time of determining the coordinatesystem exists in both the optical type inspecting apparatus 301 and theobserving apparatus 2. As a result, the coordinate system determined bythe observing apparatus 2 does not completely coincide with thecoordinate system determined by the optical type inspecting apparatus301. On account of this, even if, using directly the defects'position-coordinates 4, i.e., the output from the optical typeinspecting apparatus 301, an attempt to detect the image is made bydisplacing the stages 27 a, 27 b of the scanning type electronmicroscope, i.e., the observing apparatus 2, and displacing theobserving field-of-view, in many cases, the attempt proves to beunsuccessful in finding out the defects in the center of the observingfield-of-view.

In view of this situation, at first, limiting the defects to be detectedto the defects selected by the defect selecting unit 100 using theabove-described method, detecting the defects' image is performed. Asdescribed earlier, the selected defects are the ones the size of whichis equal to, for example, 0.7 μm or more and which are selected with theimage detecting easiness in the observing apparatus 2 employed as thecriterion. As a result, their existences can be confirmed easily even ina lower magnification of an order of guaranteeing that the defectssecurely enter the field-of-view, for example, a magnification of 10000times or less. Also, since the upper limit of the selected defects' sizehas been defined, the defects never extend off the field-of-view.

In this case, as a method of automatically recognizing the defects'positions from the detected image, as is the case with the optical typeinspecting apparatus 301, the following methods are applicable: Themethod of performing the image comparison with the use of the patterns'repeated property, or the method of recognizing the defects' positionsfrom whether the luminance of the detected image is simply brighter ordarker in comparison with the periphery thereof.

When the selected defects are unable to be detected by the observingapparatus 2 even if the above-described method is employed and executed,the defects are excluded from the selection. The defects'position-coordinates 104 determined by the observing apparatus 2 arecalculated in much the same way as the case in the 1st embodiment.

In this way, concerning the defects selected as the one that should bedetected first by the observing apparatus 2 from among the defectsdetected by the optical type inspecting apparatus 301, there can beobtained a pair of the defects' position-coordinates 4 (x, y) in theinspection target coordinate system xy determined by the optical typeinspecting apparatus 301 and the defects' position-coordinates 104 (x′,y′) in the inspection target coordinate system x′y′ determined by theobserving apparatus 2.

In much the same way as the case in the 1st embodiment, thetransformation formula from the coordinate system xy determined by theoptical type inspecting apparatus 301 to the coordinate system x′y′determined by the observing apparatus 2 is derived using a coordinategroup including these N sets of pairs (x_(i), y_(i)) (x′_(i), y′_(i))(i=1, 2, . . . , N).

Now, using the transformation formula determined in this way, all thedefects' position-coordinates 4 outputted from the optical typeinspecting apparatus 301 are transformed into the position-coordinatesin the coordinate system determined by the observing apparatus 2. Takingadvantage of the transformed position-coordinates 105, theposition-alignment of the semiconductor wafer 3 toward the coordinates'positions is performed by the stages 27 a, 27 b. Then, the imagedetection is performed with the magnification enhanced up to, forexample, 30000 times or more. This makes it possible to observe all thedetected defects in detail or to record the detailed observed image.

According to present invention toward the semiconductor wafer after thepattern's formation, it becomes possible to execute the short-time anddetailed observation of the defects, the foreign substances, or the like

Observing the defects on the semiconductor wafer is executed using thedefect inspecting method or the defect inspecting system as describedabove. This allows the cause of a defect occurrence to be discovered inthe fabrication process of semiconductor devices in an early time,thereby making it possible to obtain the semiconductor devices with anexcellent yield.

FIG. 10 is a screen diagram for illustrating an example of a screendisplay that is displayed on a monitor connected to the inspectingapparatus 1 illustrated in FIG. 2 or the optical type inspectingapparatus 301 illustrated in FIG. 9, or that is displayed on the display26 of the observing apparatus 2 illustrated in FIG. 5.

On a screen 801, a plurality of defects detected by the inspectingapparatus 1 are displayed. Moreover, position-coordinates and attributeof a defect 803 specified by a cursor 802 are displayed in a specifieddefect displaying region 805. A defect 804 existing in proximity to thedefect 803 is smaller in size than the defect 803, and thus it isdifficult for the observing apparatus 2 to detect the defect 804.Meanwhile, the defect 803 is more detectable in many cases. Thus, takingadvantage of one of the attribute of the defect 803 in proximity to thedefect 804, i.e., its larger dimension in the present example, theobserving apparatus 2 detects this defect 803 first. Once the defect 803has been detected, the defect 804 wished to be found out is easy todetect, because the defect 804 exists in proximity to the defect 803.

Next, the explanation will be given below concerning the othermodifications of the embodiments of the present invention.

As the examples of the inspecting apparatus 1, any publicly known methodor apparatus may be used as long as it makes it possible to output thedefects' position-coordinates. One example is the inspecting apparatusdisclosed in JP-A-59-192943 where, employing the semiconductor wafer orthe like as the target, the optical image is detected and the imagecomparison between the repeated patterns is performed utilizing thepatterns' repeated property, and the non-coincidences therebetween areoutputted as the defects. Of course, not being limited to thesemiconductor wafer, anything is allowable as the targets to beinspected. Such targets' examples are a mask for semiconductor, aprinted board, a ceramic board, and so on all of which are before orafter the pattern's formation. With respect to these targets, a lot ofdefect inspecting methods and systems have been known, the examples ofwhich are disclosed in the following: JP-A-59-157505, JP-A-59-232344,JP-A-2-71377, JP-A-2-100393, JP-A-55-149829, JP-A-4-216904, and so on.In the present invention, any one of these inspecting apparatuses isallowable as long as it outputs the detected defects'position-coordinates.

Also, in addition to the above-described “size”, “degree of roughness”,and “degree of serration”, the attribute of the defect assumed to beeasily detectable by the characteristic of the observing apparatus canbe used for the defect detection. As described earlier, the defect whose“degree of roughness”, i.e., the local variation in the luminance, andwhose “degree of serration”, i.e., the profile configuration, exceed acertain fixed criterion is highly likely to be a defect exposed on theinspection target surface. Consequently, when performing the inspectionoptically and the observation by an electron-beam or an ion-beam, such adefect is highly likely to be detectable in common. As a result, onlysuch defects are selected and observed, thereby allowing a wastedobserving time to be eliminated.

JP-A-4-27850 has disclosed a publicly known example of a method ofdetecting an attribute other than the above-described attribute.

Also, as the defect observing method performed subsequently to thedefect inspection, it is allowable to use any one of the publicly knownimage detecting methods or apparatuses preferable for observing thetarget defects, the examples of which are as follows: The optical imagedetecting method, the detecting method using the above-describedelectron-beam or ion-beam, the detecting method using a radiation, andso on. Concerning the detecting conditions, such as a detectingwavelength of the optical system and an accelerating voltage of theelectron-beam or the ion-beam, it is also possible to select the optimumconditions for the observation.

In all the defects' observation, designating, as ΔX, ΔY, the differencesbetween the defects' position-coordinates observed in sequence, theorder of the observation is determined so that an amount obtained bysumming up larger values out of the respective coordinate differencesΔX, ΔY becomes its minimum. This allows the observation to be executedin its minimum shortest time. Although it is not at all easy todetermine this optimum solution, it is possible to obtain itsapproximate solution by taking advantage of a technique in “CalculationGeometry” and using the same method as a method of minimizing, forexample, a pen displacing amount of a pen plotter. An example of such atechnique is described in “Calculation Geometry and GeographyInformation Processing”, Editorial Supervisor, Masao Iri, KyourituPublishing Ltd. pp. 110-121, published in 1986.

In the present invention, the defects that actually exist on thesubstrate and are easily detectable in common by the observing apparatusare selected, then being used as the criterion of the substrateposition-alignment. Consequently, even when there exists no pattern forthe position-alignment, or even when, if any, the pattern is unable tobe used in common to the inspecting apparatus and the observingapparatus, it becomes possible for the observing apparatus to executethe position-alignment toward the defects' positions with ahigh-accuracy.

On account of this, in the cases as described above, when the observingapparatus performs the observation, the collection of the observedimages, and the defect analysis toward the defects detected by theinspecting apparatus, the position-alignment toward the detected defectsis executed with a high-accuracy. This allows the images to be detectedat a time with a higher magnification, thereby resulting in an effect ofbeing able to implement the efficiency-heightening and thetime-shortening of the defect observing operation, the defect imagecollecting operation, and the defect analyzing operation.

Also, when the observing apparatus performs the observation, thecollection of the observed images, and the defect analysis toward thedefects detected by the inspecting apparatus, only the defects that aredetectable by the observing apparatus are extracted in advance by takingadvantage of the defects attribute. This, similarly, results in aneffect of being able to implement the efficiency-heightening and thetime-shortening of the defect observing operation, the defect imagecollecting operation, and the defect analyzing operation.

As a result, it becomes possible to implement the time-shortening of thefollowing operations: The observation and analysis of the foreignsubstances or crystalline defects on the semiconductor wafer before thepattern's formation, the observation and analysis of the defects or theforeign substances on the oxide film, the observation and analysis ofthe defects on the semiconductor wafer that has been subjected to aplurality of processing steps, and so on. Also, it becomes possible toautomate the collection of these defects' or foreign substances' images.

1. A defect inspecting method, comprising the steps of: detecting aplurality of defects of a semiconductor device on a substrate, andselecting desired defects from among said defects, and selecting, fromamong said defects, indicator defects that are easily detectable fromamong said plurality of defects in accordance with attribute of thedefects detected by an observing apparatus; and observing said indicatordefects by said observing apparatus in accordance with said attribute ofsaid indicator defects, and detecting said desired defects in accordancewith coordinates of said indicator defects.
 2. The defect inspectingmethod as claimed in claim 1, wherein said attribute is one of at leastdimension, type, scattered light amount, local variation in luminance,and profile configuration of said plurality of defects.
 3. A defectinspecting system comprising: a defect selecting unit for selectingdesired defects from among a plurality of defects of a semiconductordevice on a substrate detected by a defect inspecting apparatus, andselecting, from among said defects, indicator defects that are easilydetectable from among said plurality of defects in accordance withattribute of the defects detected by an observing apparatus, said defectinspecting apparatus detecting said defects of a sample, said observingapparatus observing said defects; a memory unit for storing a correlatedrelationship between defects' position-coordinates defined by saiddefect inspecting apparatus and said defects' position-coordinatesdefined by said observing apparatus; a coordinate-correspondencedetermining unit for coordinate-transforming position-coordinates ofsaid indicator defects with the use of said correlated relationship soas to calculate transformed position-coordinates of said indicatordefects, said indicator defects being detected by said observingapparatus in accordance with said attribute; and communications meansfor connecting communications among said defect selecting unit, saidmemory unit, and said coordinate-correspondence determining unit.
 4. Thedefect inspecting system as claimed in claim 3, wherein said attributeis one of at least dimension, type, scattered light amount, localvariation in luminance, and profile configuration of said plurality ofdefects.